CVE-2021-22017: VMware vCenter Server Improper Access Control
- Is it exploited?
Yes. CISA added it to the Known Exploited Vulnerabilities catalog on 10 Jan 2022, 109 days after the CVE record was published.
- How likely is exploitation in the next 30 days?
- 49.2%
EPSS score, percentile 98.9 of all scored records
- How severe?
- 5.3 Medium
CVSS v3.1 base score, from CISA's enrichment of the record
- What should I do?
CISA deadline 24 Jan 2022. Apply updates per vendor instructions.
The CVE record links no vendor advisory, patch or mitigation.
- Which versions are affected?
Affected
- VMware vCenter Server(6.7 before 6.7 U3o and 6.5 before 6.5 U3q) and VMware Clo…
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
What to do
Required action, set by CISA
Apply updates per vendor instructions.
CISA due date for this action: 24 January 2022.
Advisories and patches
The CVE record links no vendor advisory, patch or mitigation.
Linked from CISA's catalog entry
Affected products and versions
As listed in the CVE record.
| Status | Versions |
|---|---|
| Affected | VMware vCenter Server(6.7 before 6.7 U3o and 6.5 before 6.5 U3q) and VMware Clo… |
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
About this vulnerability
Rhttproxy as used in vCenter Server contains a vulnerability due to improper implementation of URI normalization.
Summary: CISA's KEV catalog, as of 28 Oct 2026.
- CISA added CVE-2021-22017 to its Known Exploited Vulnerabilities (KEV) catalog on 10 Jan 2022.
- CISA's ransomware flag for this entry is "Unknown": no evidence of ransomware use in the catalog, which is not proof of none.
- The due date CISA sets for the required action is 24 Jan 2022.
- The CVE record was published on 23 Sep 2021, 109 days before it was added to KEV.
- The CVE record carries a CVSS v3.1 base score of 5.3 (Medium), taken from CISA's enrichment of the record.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 49.2% (percentile 98.9), as of 28 Oct 2026.
- CISA's SSVC assessment in the CVE record: exploitation active, automatable yes, technical impact partial.
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026. About the data.
Description
Rhttproxy as used in vCenter Server contains a vulnerability due to improper implementation of URI normalization. A malicious actor with network access to port 443 on vCenter Server may exploit this issue to bypass proxy leading to internal endpoints being accessed.
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
Weakness
CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record and the KEV entry.
Timeline
| Date | Event |
|---|---|
| 23 Sep 2021 | CVE record published |
| 10 Jan 2022 | Added to CISA KEV |
| 24 Jan 2022 | CISA due date for the required action |
| 21 Oct 2025 | CVE record last updated |
References
More exploited VMware vulnerabilities
- CVE-2025-22224: VMware ESXi and Workstation TOCTOU Race Condition Vulnerability
- CVE-2025-22225: VMware ESXi Arbitrary Write Vulnerability
- CVE-2025-22226: VMware ESXi, Workstation, and Fusion Information Disclosure Vulnerability
- CVE-2024-38812: VMware vCenter Server Heap-Based Buffer Overflow Vulnerability
- CVE-2024-38813: VMware vCenter Server Privilege Escalation Vulnerability
- CVE-2024-37085: VMware ESXi Authentication Bypass Vulnerability